Abstract
Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex vivo imaging of breast tumour samples revealed excellent contrast between lowly birefringent malignant regions, and stromal tissue, which is rich in oriented collagen and exhibits higher birefringence, as confirmed with co-located histology. The ability to clearly differentiate between tumour and uninvolved stroma based on intrinsic contrast could prove decisive for the intraoperative assessment of tumour margins.
Highlights
SMF NCF GRIN NCF, 48 ̊, angle polished including in breast tumour samples[9]
These results demonstrate the potential of using intrinsic tissue birefringence as a biomarker to differentiate between healthy tissue and tumour, which could aid in the intraoperative assessment of breast tumour margins
Breast tissue contains lobules of alveolar glands and ducts that are supported by a dense fibrous connective tissue, termed fibrous stroma, and lipid-filled adipocytes in varying proportions
Summary
SMF NCF GRIN NCF, 48 ̊, angle polished including in breast tumour samples[9]. In breast tissue, it is straightforward to identify adipose tissue due to its characteristic structural signal[10]. Passively depth-encoded PS-OCT system to interface with our imaging needles, and developed a novel reconstruction method based on the Mueller formalism: Mueller matrices were constructed from their corresponding measured Jones matrices and incoherently averaged before extracting the local retardation using the differential Mueller formalism[34,35] This approach overcomes difficulties with averaging in the coherent Jones formalism and results in improved and robust measurements of depth-resolved tissue birefringence. Imaging fresh, excised tumour specimens with needle-based PS-OCT, we found compelling contrast between more highly birefringent uninvolved stroma and lowly birefringent malignant regions, which we confirmed with spatially co-registered histology These results demonstrate the potential of using intrinsic tissue birefringence as a biomarker to differentiate between healthy tissue and tumour, which could aid in the intraoperative assessment of breast tumour margins
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